U.S. patent application number 13/212037 was filed with the patent office on 2013-02-21 for method and system of fabricating pzt nanoparticle ink based piezoelectric sensor.
This patent application is currently assigned to University of Washington through its Center for Commercialization. The applicant listed for this patent is Guozhong Cao, Jeffrey Lynn Duce, Hsien-Lin Huang, Scott Robert Johnston, I-Yeu Shen. Invention is credited to Guozhong Cao, Jeffrey Lynn Duce, Hsien-Lin Huang, Scott Robert Johnston, I-Yeu Shen.
Application Number | 20130044175 13/212037 |
Document ID | / |
Family ID | 46682694 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130044175 |
Kind Code |
A1 |
Duce; Jeffrey Lynn ; et
al. |
February 21, 2013 |
Method and System of Fabricating PZT Nanoparticle Ink Based
Piezoelectric Sensor
Abstract
The disclosure provides in one embodiment a method of
fabricating a lead zirconate titanate (PZT) nanoparticle ink based
piezoelectric sensor. The method has a step of formulating a lead
zirconate titanate (PZT) nanoparticle ink. The method further has a
step of depositing the PZT nanoparticle ink onto a substrate via an
ink deposition process to form a PZT nanoparticle ink based
piezoelectric sensor.
Inventors: |
Duce; Jeffrey Lynn; (Milton,
WA) ; Johnston; Scott Robert; (St. Louis, MO)
; Shen; I-Yeu; (Seattle, WA) ; Cao; Guozhong;
(Seattle, WA) ; Huang; Hsien-Lin; (Lynnwood,
WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Duce; Jeffrey Lynn
Johnston; Scott Robert
Shen; I-Yeu
Cao; Guozhong
Huang; Hsien-Lin |
Milton
St. Louis
Seattle
Seattle
Lynnwood |
WA
MO
WA
WA
WA |
US
US
US
US
US |
|
|
Assignee: |
University of Washington through
its Center for Commercialization
Seattle
WA
The Boeing Company
Seal Beach
CA
|
Family ID: |
46682694 |
Appl. No.: |
13/212037 |
Filed: |
August 17, 2011 |
Current U.S.
Class: |
347/110 ;
101/483 |
Current CPC
Class: |
G01L 1/16 20130101; H01L
41/0805 20130101; H01L 41/1132 20130101; H01L 41/1876 20130101;
G01M 5/0083 20130101; H01L 41/314 20130101; G01M 5/0033
20130101 |
Class at
Publication: |
347/110 ;
101/483 |
International
Class: |
B41J 2/00 20060101
B41J002/00 |
Claims
1. A method of fabricating a lead zirconate titanate (PZT)
nanoparticle ink based piezoelectric sensor, the method comprising:
formulating a lead zirconate titanate (PZT) nanoparticle ink; and,
depositing the PZT nanoparticle ink onto a substrate via an ink
deposition process to form a PZT nanoparticle ink based
piezoelectric sensor.
2. The method of claim 1, wherein the PZT nanoparticle ink
comprises nanoscale PZT particles.
3. The method of claim 1, wherein the PZT nanoparticle ink
comprises a sol-gel based adhesion promoter for promoting adhesion
of the PZT nanoparticle ink to the substrate.
4. The method of claim 1, wherein the ink deposition process does
not require PZT crystal growth on the substrate.
5. The method of claim 1, wherein the ink deposition process
comprises a direct write printing process selected from a group
comprising a jetted atomized deposition process, an ink jet
printing process, an aerosol printing process, a pulsed laser
evaporation process, a flexography printing process, a micro-spray
printing process, a flat bed silk screen printing process, a rotary
silk screen printing process, and a gravure printing process.
6. The method of claim 1, wherein the substrate comprises a
material selected from a group comprising a composite material, a
metallic material, and a combination of a composite material and a
metallic material.
7. The method of claim 1, wherein the substrate has a curved
surface.
8. The method of claim 1, wherein the PZT nanoparticle ink based
piezoelectric sensor is deposited onto the substrate in a
customized shape.
9. A method of fabricating a lead zirconate titanate (PZT)
nanoparticle ink based piezoelectric sensor, the method comprising:
formulating a lead zirconate titanate (PZT) nanoparticle ink
comprising pre-crystallized PZT nanoparticles; suspending the PZT
nanoparticle ink in a sol-gel based adhesion promoter; and,
depositing the PZT nanoparticle ink onto a substrate via a direct
write printing process to form a PZT nanoparticle ink based
piezoelectric sensor.
10. The method of claim 9, wherein the PZT nanoparticle ink
comprises nanoscale PZT particles.
11. The method of claim 9, wherein the direct write printing
process does not require PZT crystal growth on the substrate.
12. The method of claim 9, wherein the direct write printing
process is a process selected from a group comprising selected from
a group comprising a jetted atomized deposition process, an ink jet
printing process, an aerosol printing process, a pulsed laser
evaporation process, a flexography printing process, a micro-spray
printing process, a flat bed silk screen printing process, a rotary
silk screen printing process, and a gravure printing process.
13. A system for fabricating a lead zirconate titanate (PZT)
nanoparticle ink based piezoelectric sensor, the system comprising:
a formulated lead zirconate titanate (PZT) nanoparticle ink; and,
an ink deposition apparatus depositing the PZT nanoparticle ink
onto a substrate to form a PZT nanoparticle ink based piezoelectric
sensor.
14. The system of claim 13, wherein the PZT nanoparticle ink
comprises nanoscale PZT particles.
15. The system of claim 13, wherein the PZT nanoparticle ink
comprises a sol-gel based adhesion promoter for promoting adhesion
of the PZT nanoparticle ink to the surface of the substrate.
16. The system of claim 13, wherein the ink deposition apparatus
does not require PZT crystal growth on the surface of the
substrate.
17. The system of claim 13, wherein the ink deposition apparatus
comprises a direct write printing apparatus selected from a group
comprising a jetted atomized deposition apparatus, an ink jet
printing apparatus, an aerosol printing apparatus, a pulsed laser
evaporation apparatus, a flexography printing apparatus, a
micro-spray printing apparatus, a flat bed silk screen printing
apparatus, a rotary silk screen printing process, and a gravure
printing process.
18. The system of claim 13, wherein the substrate comprises a
material selected from a group comprising a composite material, a
metallic material, and a combination of a composite material and a
metallic material.
19. The system of claim 13, wherein the substrate is curved.
20. The system of claim 13, wherein the PZT nanoparticle ink based
piezoelectric sensor is deposited onto the substrate in a
customized shape.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This nonprovisional patent application is related to
contemporaneously filed U.S. nonprovisional patent application Ser.
No. 13/211,554, titled "METHODS FOR FORMING LEAD ZIRCONATE TITANATE
NANOPARTICLES", having Attorney Docket Number UWOTL-1-37259, filed
on Aug. 17, 2011, and this nonprovisional patent application is
also related to contemporaneously filed U.S. nonprovisional patent
application Ser. No. ______, titled "METHOD AND SYSTEM FOR
DISTRIBUTED NETWORK OF NANOPARTICLE INK BASED PIEZOELECTRIC SENSORS
FOR STRUCTURAL HEALTH MONITORING", having Attorney Docket Number
11-0839-US-NP, filed on Aug. 17, 2011. The contents of both of
these contemporaneously filed U.S. nonprovisional patent
applications are hereby incorporated by reference in their
entireties.
BACKGROUND
[0002] 1) Field of the Disclosure
[0003] The disclosure relates generally to methods and systems of
fabricating sensors, and more particularly, to methods and systems
for fabricating nanoparticle piezoelectric sensors deposited onto a
structure.
[0004] 2) Description of Related Art
[0005] Small sensors, such as microsensors, may be used in a
variety of applications including in structural health monitoring
(SHM) systems and methods to continuously monitor structures, such
as composite or metal structures, and to measure material
characteristics and stress and strain levels in order to assess
performance, possible damage, and current state of the structures.
Known SHM systems and methods may include the use of small, stiff,
ceramic disk sensors integrated onto a polyimide substrate and
connected to power and communication wiring. Such known sensors are
typically manually bonded to a structure with an adhesive. Such
manual installation may increase labor and installation costs and
such adhesive may degrade over time and may result in the sensor
disbonding from the structure. In addition, such known sensors may
be made of rigid, planar, and/or brittle materials that may limit
their usage, for example, usage on a curved or non-planar substrate
surface may be difficult. Moreover, in a large array of such known
sensors, the amount of power and communication wiring required may
increase the complexity and the weight of the structure.
[0006] In addition, known sensor systems and methods, such as
micro-electromechanical systems (MEMS) and methods, may include the
use of depositing onto a substrate piezoelectric sensors, such as
lead zirconate titanate (PZT) sensors, having nanoparticles. Known
methods for making such MEMS may include molten salt synthesis of
PZT powder for direct write inks. However, the applications of the
PZT sensors fabricated with such known methods may be limited by
the physical geometry of the PZT sensors. Such physical geometry
limitations may result in inadequate sensing capacities or
inadequate actuation responses. Further, the PZT sensors fabricated
with such known methods may be unable to be applied or located in
areas where their function may be important due to the PZT sensor
fabrication method. For example, known molten salt synthesis
methods may require processing at higher temperatures than certain
application substrates can tolerate.
[0007] Further, such known MEMS systems and methods may also
include the use of sensors having nanoparticles which have not been
crystallized and which may be less efficient than nanoparticles
which have been crystallized. Non-crystallized structures typically
have greater disorganization resulting in decreased response
sensitivity to strain and voltage, whereas crystallized structures
typically have greater internal organization resulting in increased
response sensitivity to strain and decreased necessity for energy
to operate. In addition, the nanoparticles of the sensors may be
too large for some known deposition processes and systems, such as
a jetted atomized deposition (JAD) process, and such nanoparticles
may require a high temperature sintering/crystallization process
which may result in damage to temperature sensitive substrates or
structures.
[0008] Accordingly, there is a need in the art for an improved
method and system of fabricating PZT piezoelectric sensors having
nanoparticles that may be used in structural health monitoring
systems and methods for structures, where such improved method and
system provide advantages over known methods and systems.
SUMMARY
[0009] This need for a method and system of fabricating lead
zirconate titanate (PZT) piezoelectric sensors having nanoparticles
that may be used in structural health monitoring systems and
methods for structures is satisfied. As discussed in the below
detailed description, embodiments of the method and system may
provide significant advantages over existing methods and
systems.
[0010] In an embodiment of the disclosure, there is provided a
method of fabricating a lead zirconate titanate (PZT) nanoparticle
ink based piezoelectric sensor. The method comprises formulating a
PZT nanoparticle ink. The method further comprises depositing the
PZT nanoparticle ink onto a substrate via an ink deposition process
to form a PZT nanoparticle ink based piezoelectric sensor.
[0011] In another embodiment of the disclosure, there is provided a
method of fabricating a lead zirconate titanate (PZT) nanoparticle
ink based piezoelectric sensor. The method comprises formulating a
PZT nanoparticle ink comprising pre-crystallized PZT nanoparticles.
The method further comprises suspending the PZT nanoparticle ink in
a sol-gel based adhesion promoter. The method further comprises
depositing the PZT nanoparticle ink onto a substrate via a direct
write printing process to form a PZT nanoparticle ink based
piezoelectric sensor.
[0012] In another embodiment of the disclosure, there is provided a
system for fabricating a lead zirconate titanate (PZT) nanoparticle
ink based piezoelectric sensor. The system comprises a formulated
PZT nanoparticle ink. The system further comprises an ink
deposition apparatus depositing the PZT nanoparticle ink onto a
substrate to form a PZT nanoparticle ink based piezoelectric
sensor. The structure may have a non-curved or planar surface, a
curved or non-planar surface, or a combination of a non-curved or
planar surface and a curved or non-planar surface. The PZT
nanoparticle ink based piezoelectric sensor may be deposited onto a
surface of the structure with one or more layers of insulation,
coatings, or paint in between a body of the structure and the PZT
nanoparticle ink based piezoelectric sensor.
[0013] The features, functions, and advantages that have been
discussed can be achieved independently in various embodiments of
the disclosure or may be combined in yet other embodiments further
details of which can be seen with reference to the following
description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The disclosure can be better understood with reference to
the following detailed description taken in conjunction with the
accompanying drawings which illustrate preferred and exemplary
embodiments, but which are not necessarily drawn to scale,
wherein:
[0015] FIG. 1 is an illustration of a perspective view of an
exemplary aircraft for which one of the embodiments of the system
and method of the disclosure may be used;
[0016] FIG. 2 is an illustration of a cross-sectional view of one
of the embodiments of a deposited PZT nanoparticle ink based
piezoelectric sensor assembly;
[0017] FIG. 3 is an illustration of a cross-sectional view of
another one of the embodiments of a deposited PZT nanoparticle ink
based piezoelectric sensor assembly;
[0018] FIG. 4 is an illustration of a top perspective view of one
of the embodiments of a deposited PZT nanoparticle ink based
piezoelectric sensor assembly deposited on a composite
structure;
[0019] FIG. 5 is an illustration of a block diagram of one of the
embodiments of a system for fabricating a PZT nanoparticle ink
based piezoelectric sensor of the disclosure;
[0020] FIG. 6A is an illustration of a schematic view of one of the
embodiments of an ink deposition process and apparatus for
fabricating a PZT nanoparticle ink based piezoelectric sensor of
the disclosure;
[0021] FIG. 6B is an illustration of a close-up view of the PZT
piezoelectric nanoparticle ink based sensor being deposited on the
substrate;
[0022] FIG. 7 is an illustration of a schematic diagram of one of
the embodiments of a structural health monitoring system using the
PZT nanoparticle ink based piezoelectric sensors of the
disclosure;
[0023] FIG. 8 is an illustration of a flow diagram of an embodiment
of a method of the disclosure;
[0024] FIG. 9 is an illustration of a flow diagram of another
embodiment of a method of the disclosure; and,
[0025] FIG. 10 is an illustration of a block diagram of embodiments
of the ink deposition processes and ink deposition apparatuses that
may be used to fabricate the PZT nanoparticle ink based
piezoelectric sensor of the disclosure.
DETAILED DESCRIPTION
[0026] Disclosed embodiments will now be described more fully
hereinafter with reference to the accompanying drawings, in which
some, but not all of the disclosed embodiments are shown. Indeed,
several different embodiments may be provided and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete and will fully convey the scope of the
disclosure to those skilled in the art. The following detailed
description is of the best currently contemplated modes of carrying
out the disclosure. The description is not to be taken in a
limiting sense, but is made merely for the purpose of illustrating
the general principles of the disclosure, since the scope of the
disclosure is best defined by the appended claims.
[0027] Now referring to the Figures, FIG. 1 is an illustration of a
perspective view of an exemplary prior art aircraft 10 for which
one of the embodiments of a system 100 (see FIG. 5), a method 200
(see FIG. 8), or a method 250 (see FIG. 9), for fabricating a lead
zirconate titanate (PZT) nanoparticle ink based piezoelectric
sensor 110 (see FIG. 2) for a structure 30, such as composite
structure 102 (see FIG. 1) or a metallic structure 132 (see FIG.
3), may be used. As used herein, the term "PZT" means lead
zirconate titanate--a piezoelectric, ferroelectric, ceramic
material composed of the chemical elements lead and zirconium and
the chemical compound titanate which may be combined under high
temperatures. PZT exhibits favorable piezoelectric properties. As
used herein, the term "piezoelectric" in relation to PZT means that
PZT develops a voltage or potential difference across two of its
faces when deformed, which is advantageous for sensor applications,
or it physically changes shape when an external electric field is
applied, which is advantageous for actuator applications. For
purposes of this application, the term "ferroelectric" in relation
to PZT means PZT has a spontaneous electric polarization or
electric dipole which can be reversed in the presence of an
electric field.
[0028] The aircraft 10 comprises a fuselage 12, a nose 14, a
cockpit 16, wings 18 operatively coupled to the fuselage 12, one or
more propulsion units 20, a tail vertical stabilizer 22, and one or
more tail horizontal stabilizers 24. Although the aircraft 10 shown
in FIG. 1 is generally representative of a commercial passenger
aircraft, the system 100 and methods 200, 250 disclosed herein may
also be employed in other types of aircraft. More specifically, the
teachings of the disclosed embodiments may be applied to other
passenger aircraft, cargo aircraft, military aircraft, rotorcraft,
and other types of aircraft or aerial vehicles, as well as
aerospace vehicles such as satellites, space launch vehicles,
rockets, and other types of aerospace vehicles. It may also be
appreciated that embodiments of systems, methods and apparatuses in
accordance with the disclosure may be utilized in other vehicles,
such as boats and other watercraft, trains, automobiles, trucks,
buses, and other types of vehicles. It may also be appreciated that
embodiments of systems, methods and apparatuses in accordance with
the disclosure may be utilized in architectural structures, turbine
blades, medical devices, electronic actuation equipment, consumer
electronic devices, vibratory equipment, passive and active
dampers, or other suitable structures.
[0029] In an embodiment of the disclosure, there is provided a
system 100 for fabricating the lead zirconate titanate (PZT)
nanoparticle ink based piezoelectric sensor 110. FIG. 5 is an
illustration of a block diagram of one of the embodiments of the
system 100 for fabricating the PZT nanoparticle ink based
piezoelectric sensor 110 (see also FIG. 2) of the disclosure. As
shown in FIG. 5, the system 100 for fabricating the PZT
nanoparticle ink based piezoelectric sensor 110 comprises a
formulated lead zirconate titanate (PZT) nanoparticle ink 104. The
PZT nanoparticle ink 104 comprises nanoscale PZT ink particles or
nanoparticles 106. Preferably, the nanoscale PZT ink nanoparticles
are pre-crystallized. The PZT nanoparticle ink 104 preferably has a
nanoscale PZT particle size in a range of from about 20 nanometers
to about 1 micron. The nanoscale PZT ink particles size allows for
the PZT nanoparticle ink 104 to be deposited using a wide range of
ink deposition processes, apparatuses, and systems, and in
particular, allows for the PZT nanoparticle ink 104 to be deposited
using a jetted atomized deposition process 126 (see FIGS. 6A and
10) system and a jetted atomized deposition apparatus 146 (see
FIGS. 6A and 10). The PZT nanoparticle ink based piezoelectric
sensor 110 may have a thickness in a range of from about 1 micron
to about 500 microns. The thickness of the PZT nanoparticle ink
based piezoelectric sensor 110 may be measured in terms of a factor
of nanoparticle size of the PZT nanoparticles and the thickness of
conductive electrodes 114, 118 (see FIG. 2). Thickness of the PZT
nanoparticle ink based piezoelectric sensor 110 may also depend on
the size of the PZT nanoparticle ink based piezoelectric sensor
110, as a proper aspect ratio may increase the sensitivity of the
PZT nanoparticle ink based piezoelectric sensor 110.
[0030] The PZT nanoparticle ink 104 may further comprise a sol-gel
based adhesion promoter 108 (see FIG. 5) for promoting adhesion of
the PZT nanoparticle ink 104 to a substrate 101. Alternatively, the
PZT nanoparticle ink 104 may further comprise a polymer based
adhesion promoter such as an epoxy or another suitable polymer
based adhesion promoter. The nanoscale PZT ink nanoparticles 106
may be suspended in a silica sol-gel and then deposited using an
ink deposition process 122 such as a direct write printing process
124. The silica sol-gel in the PZT nanoparticle ink formulation
enables the PZT nanoparticle ink 104 to bond to a wider variety of
substrates than certain known adhesion promoters. The PZT
nanoparticle ink based piezoelectric sensor 110 preferably has
modalities based on ultrasonic wave propagation and
electromechanical impedance.
[0031] The formulated lead zirconate titanate (PZT) nanoparticle
ink 104 may be formulated by methods disclosed in contemporaneously
filed U.S. nonprovisional patent application Ser. No. 13/211,554,
titled "METHODS FOR FORMING LEAD ZIRCONATE TITANATE NANOPARTICLES",
having Attorney Docket Number UWOTL-1-37259, filed on Aug. 17,
2011, which is hereby incorporated by reference in its
entirety.
[0032] In particular, in such disclosure, methods for forming lead
zirconate titanate (PZT) nanoparticles are provided. The PZT
nanoparticles are formed from a precursor solution--comprising a
source of lead, a source of titanium, a source of zirconium, and a
mineraliser--that undergoes a hydrothermal process according to the
following reaction ("the hydrothermal process"):
Pb.sup.2++xTiO.sub.2+(1-x)ZrO.sub.2+2OH.sup.-PbTi.sub.xZr.sub.1-xO.sub.3-
+H.sub.2O
[0033] In the provided methods, the properties of the formed PZT
nanoparticles are dictated at least by the mineraliser
concentration, processing time, heating rate, and cooling rate.
[0034] In one aspect, a method is provided for forming a plurality
of PZT nanoparticles (also referred to herein as "nanocrystals").
In one embodiment, the method includes the steps of: (a) providing
an aqueous precursor solution comprising a mineraliser solution, a
source of titanium, a source of zirconium, and a source of lead;
and (b) heating the precursor solution to produce PZT
nanoparticles, wherein heating the precursor solution comprises a
first heating schedule that includes at least the sequential steps
of: (i) heating the precursor solution at a first rate to a first
temperature, wherein said first rate is between about 1.degree.
C./min (degrees Celsius per minute) and about 30.degree. C./min,
and wherein said first temperature is between about 120.degree. C.
and about 350.degree. C.; (ii) holding for a first hold time at the
first temperature, wherein said first hold time is between about 5
to about 300 minutes; and (iii) cooling at a second rate to provide
a nanoparticle PZT solution comprising a suspended plurality of
perovskite PZT nanoparticles having a smallest dimension of between
about 20 nm (nanometer) and about 1000 nm, wherein said second rate
is between about 1.degree. C./min and about 30.degree. C./min.
[0035] Precursor Solution.
[0036] The precursor solution is defined by reactants that are
processed to form PZT nanoparticles. Specifically, the precursor
solution includes at least a source of titanium, a source of
zirconium, a source of lead, and a mineraliser. The precursor
solution optionally includes additional solvents or stabilizers, as
will be discussed in more detail below.
[0037] The components of the precursor solution may all be combined
simultaneously in a single reaction vessel, or may be combined
stepwise, depending on the character of the components of the
precursor solution and a potential need to minimize interaction
between the components of the precursor prior to hydrothermal
reaction to produce PZT nanoparticles. For example, the source of
titanium and the source of zinc may be combined to form a precursor
gel, which is then combined with a source of lead in aqueous form
and the mineraliser to provide the precursor solution. Such an
approach allows for maximum control over the relative molar amounts
of each of the reactants (i.e., the sources of titanium, zirconium,
and lead).
[0038] The sources of lead, titanium, and zirconium are present in
the precursor solution in molar amounts sufficient to obtain PZT
nanoparticles having the formula Pb.sub.xZi.sub.yTi.sub.zO.sub.3,
wherein x is between 0.8 and 2, wherein y is between 0.4 and 0.6,
and wherein y plus z equals 1. For example, a common formula for
perovskite PZT nanoparticles is Pb(Zr.sub.0.52Ti.sub.0.48)O.sub.3.
However, it will be appreciated by those of skill in the art that
the relative amounts of lead, zirconium, and titanium can be
modified within the provided ranges to produce the desired
characteristics of PZT nanoparticles.
[0039] The source of titanium in the precursor solution can be any
titanium-containing compound that allows for the formation of PZT
particles according to the method provided herein. In one
embodiment, the source of titanium is
Ti[OCH(CH.sub.3).sub.2].sub.4. Additional sources of titanium may
comprise TiO.sub.2, TiO.sub.2*nH.sub.2O, Ti(OC.sub.4H.sub.9),
Ti(NO.sub.3).sub.2, TiCl.sub.3, TiCl.sub.4.
[0040] The source of zirconium in the precursor solution can be any
zirconium-containing compound that allows for the formation of PZT
particles according to the method provided herein. In one
embodiment, the source of zirconium is
Zr[O(CH.sub.2).sub.2CH.sub.3].sub.4. Additional sources of
zirconium may comprise Zr(NO.sub.3).sub.4*5H.sub.2O,
ZrOCl.sub.2*8H.sub.2O, ZrO.sub.2*nH.sub.2O, ZrO.sub.2.
[0041] The source of lead in the precursor solution can be any
lead-containing compound that allows for the formation of PZT
particles according to the method provided herein. In one
embodiment, the source of lead is Pb(CH.sub.3COOH).sub.2.
Additional sources of lead may comprise Pb(NO.sub.3).sub.2,
Pb(OH).sub.2, PbO, Pb.sub.2O.sub.3, PbO.sub.2.
[0042] In certain embodiments, excess lead is added to the
precursor solution. As used herein, the term "excess lead" refers
to a ratio amount greater than one for the source of lead. Excess
lead is a means for exerting further control over the
characteristics of the PZT nanoparticles. Typically, the excess
lead is achieved in the precursor solution by adding an excess
amount of the same source of lead as described above. For example,
if the source of lead is lead acetate trihydrate, any amount of
lead acetate trihydrate added to the precursor solution that
results in the ratio of the lead acetate trihydrate to be greater
than one compared to the source of zirconium and the source of
titanium will be considered an excess amount of lead. In certain
embodiments, the excess amount of lead comes from a second,
different, source of lead.
[0043] Excess lead does not alter the chemical composition of the
PZT nanoparticles, but instead modifies the hydrothermal reaction
conditions to produce several desirable effects on the formed PZT
nanoparticles. While the excess lead does not alter the fundamental
crystal structure of the PZT nanoparticles, it improves morphology,
reduces amorphous byproducts, and reduces the degree of
agglomeration between particles.
[0044] One less desirable side effect of excess lead is that it
also leads to the formation of a lead oxide compound that is an
impurity. However, the lead oxide impurity can be removed by
washing the formed PZT nanoparticles with an appropriate solvent
(e.g., diluted acetic acid).
[0045] The mineraliser in the precursor solution facilitates the
formation of PZT during the hydrothermal process. The mineraliser
acts as a source of hydroxide ions to facilitate the hydrothermal
synthesis of PZT. Representative mineralisers include KOH, NaOH,
LiOH, NH.sub.4OH, and combinations thereof. The concentration of
the mineraliser, in a mineraliser solution prior to adding to the
other components of the precursor solution, is from about 0.2 M to
about 15 M if the mineraliser is liquid such as NaOH. If the
mineraliser is solid, such as KOH, DI water is first added into the
Zr, Ti, Pb mixture and then the solid mineraliser is added. The
optimal mineraliser concentration depends on the conditions of the
hydrothermal process, as is known to those of skill in the art.
[0046] The concentration of the mineraliser affects the size of PZT
nanoparticles produced. For example, similar PZT nanoparticles
formed using 5 M and 10 M KOH mineraliser have similar morphology,
but 5 M mineraliser results in smaller nanoparticles than those
formed with 10 M mineraliser, if all other processing conditions
are the same.
[0047] In certain embodiments, a stabilizer is added to the
precursor to prevent gelation and/or precipitation of certain
components of the precursor prior to the hydrothermal process. That
is, stabilizers may be required to maintain all of the necessary
components of the precursor in solution prior to the hydrothermal
process. For example, in one embodiment, acetylacetone ("AcAc") is
added to the source of titanium (e.g., titanium isopropoxide) to
prevent gelation and precipitation prior to reaction to form PZT.
In another embodiment, propoxide is added to the source of
titanium.
[0048] The precursor solution is typically aqueous, although it
will be appreciated that any other solvent capable of solvating the
components of the precursor solution and facilitating the formation
of PZT nanoparticles can also be used. Alternatives to water may
comprise aqueous solution, mixture of water and organic solvent, or
weak organic acid, for example, ethylenediamine, CH.sub.2Cl.sub.2,
ammonium salt, acetic acid or another suitable alternative.
[0049] In an exemplary embodiment, the precursor solution comprises
KOH as the mineraliser solution, titanium isopropoxide as the
source of titanium, zirconium n-propoxide as the source of
zirconium, lead acetate trihydrate as the source of lead,
acetylacetone as a stabilizer, and water. The lead acetate
trihydrate, zirconium n-propoxide, and titanium isopropoxide are
present in the precursor in a weight ratio of from about 1 to about
2 parts lead acetate trihydrate, from about 0.5 to about 1 parts
zirconium n-propoxide, and from about 0.8 to about 1.6 parts
titanium isopropoxide. The KOH mineraliser solution is from about
0.2 to about 15M.
[0050] Heating Schedule.
[0051] PZT nanoparticles are formed through hydrothermal processing
of the precursor solution. The hydrothermal process includes a
heating schedule comprising a heating ramp to a first temperature,
a hold at the first temperature, and a cooling ramp to room
temperature.
[0052] The heating schedule is performed under pressure greater
than 1 atm (atmosphere). Accordingly, the precursor solution is
contained within an apparatus configured to both heat and
pressurize. In certain embodiments, the pressure applied during the
heating schedule is from about 1 atm to about 20 atm. In an
exemplary embodiment, the precursor solution is contained within an
autoclave and autogenous pressure builds in the autoclave over the
course of the heating schedule. Alternatively, a constant pressure
can be provided by a pump or other apparatus known to those of
skill in the art.
[0053] In one embodiment, heating the precursor solution to produce
PZT nanoparticles includes at least the sequential steps of: (i)
heating the precursor solution at a first rate to a first
temperature, wherein said first rate is between about 1.degree.
C./min (degrees Celsius per minute) and about 30.degree. C./min,
and wherein said first temperature is between about 120.degree. C.
and about 350.degree. C.; (ii) holding for a first hold time at the
first temperature, wherein said first hold time is between about 5
minutes to about 300 minutes; and, (iii) cooling at a second rate
to provide a nanoparticle PZT solution comprising a suspended
plurality of perovskite PZT nanoparticles having a smallest
dimension of between about 20 nm (nanometers) and about 1000 nm,
wherein said second rate is between about 1.degree. C./min and
about 30.degree. C./min.
[0054] The heating ramp rate ("first rate") is used to raise the
temperature of the precursor solution from about room temperature
(T.sub.RT) to the maximum hydrothermal processing temperature
(T.sub.max). The first rate is from about 1.degree. C./min and
about 30.degree. C./min.
[0055] The processing temperature ("first temperature"; T.sub.max)
is between about 120.degree. C. (Celsius) and about 350.degree. C.
In certain embodiments, the first temperature is 200.degree. C. or
less. While the heating schedule is primarily described herein as
including a single first temperature, to which the solution is
heated, it will be appreciated that the disclosed method
contemplates variations in the first temperature that may arise
from the hydrothermal reaction or inaccuracies in the heating
equipment. Furthermore, the heating step of the heating schedule
may include second, third, or further, temperatures to which the
heated precursor solution is subjected. The second, third, or
further temperatures may be higher or lower than the first
temperature, as required to produce the desired PZT
nanoparticles.
[0056] The first rate is particularly important to control the size
of the PZT nanoparticles produced. In this regard, as the
temperature of the precursor solution heats from T.sub.RT to
T.sub.max, there is an intermediate temperature, T.sub.nuc, at
which PZT crystals begin to nucleate ("Nucleation Zone"). Optimal
PZT crystal growth occurs at T.sub.max, and any crystals nucleated
at a temperature lower than T.sub.max will likely grow larger with
bigger aggregates and/or higher degree of agglomeration than PZT
crystals nucleated at T.sub.max.
[0057] A slow ramp rate results in a longer amount of time that the
precursor solution spends between T.sub.nuc and T.sub.max.
Accordingly, a slow ramp rate results in more PZT crystal
nucleation at temperatures below T.sub.max, resulting in
inconsistent PZT crystal size and crystal structure. As used
herein, the term "slow ramp rate" refers to a ramp rate of below
1.degree. C./min.
[0058] Conversely, a relatively fast ramp rate results in
homogeneous PZT crystal nucleation by passing the precursor
solution quickly through the temperature range between T.sub.nuc
and T.sub.max. As used herein, the term "fast ramp rate" refers to
a ramp rate of 10.degree. C./min or greater. In certain
embodiments, the high ramp rate is a ramp rate of 20.degree. C./min
or greater.
[0059] As a result of the nucleation dynamics described above, the
higher the ramp rate, the smaller the PZT particles generated.
While the heating ramp rate affects the size and number of PZT
crystals, it does not affect the crystal structure. Similarly, the
cooling rate does not affect the crystal structure.
[0060] The "hold" step of the heating schedule allows the PZT
crystals time to form and grow. The hold step is between about 5
minutes and about 300 minutes at the first temperature. Typically,
a longer hold time results in larger crystals. Holding time is
preferably to allow the crystals to grow. If the holding time is
too short, the end product may not have PZT composition.
[0061] After the hold step, the heating schedule proceeds to a
"cooling" step. The cooling rate reduces the temperature from the
maximum processing temperature to room temperature at a "second
rate." The range of the cooling rate is from about 1.degree. C./min
to about 30.degree. C./min. The cooling rate impacts several
aspects of the PZT nanoparticles. The cooling rate partially
determines the morphology and size of the formed PZT nanoparticles.
A relatively fast cooling rate, for example, a cooling rate of
greater than 20.degree. C. per minute, results in PZT nanoparticles
in the range of 100 nm to 500 nm and a distinct cubic shape.
[0062] Additionally, a relatively fast cooling rate results in PZT
nanoparticles that are physically bonded, as opposed to chemically
bonded. Physically bonded PZT nanoparticles are preferable to those
that are chemically bonded because separation of physically bonded
nanoparticles is accomplished more readily than the separation of
chemically bonded nanoparticles (e.g., by mechanical agitation).
Finally, a faster cooling rate minimizes the presence of
PbTiO.sub.3 phase in the final product. This is desirable because
PbTiO.sub.3 not only is an impurity that must be removed to obtain
pure PZT nanoparticles, but forming PbTiO.sub.3 also reduces the
yield of the PZT-formation reaction by consuming lead and titanium
in a form other than PZT.
[0063] In certain embodiments, the second rate is sufficiently
large that PZT particles are formed that are non-perovskite forms
of PZT. In this regard, in certain embodiments, the method further
comprises a step of treating the nanoparticle PZT solution to
eliminate the non-perovskite forms of PZT. Such a treatment may
include chemically-assisted dissolution, wet etching, acid washing,
base washing, and combinations thereof. Any method that selectively
eliminates (e.g., dissolves) the non-perovskite PZT can be used.
For example, a dilute acetic acid wash can be used to eliminate the
PbTiO.sub.3 non-perovskite component of the PZT hydrothermal
synthesis.
[0064] Alternatively, instead of eliminating the non-perovskite PZT
particles, in certain embodiments, the method further includes a
step of separating the perovskite PZT nanoparticles from the
non-perovskite forms of PZT in the nanoparticle PZT solution. The
end suspension is washed with DI water, diluted acid, or ethanol to
remove the non-perovskite forms.
[0065] In certain embodiments, the second rate is sufficiently
large that the nanoparticle PZT solution becomes supersaturated.
Nucleation and crystal growth is allowed when the solution is
supersaturated and they stop when the concentration reaches to an
equilibrium. For all temperatures, there is an equilibrium
concentration responses to it. Therefore, when the second rate is
slow, the solution can be supersaturated multiple times and the
crystal can have a greater opportunity to grow bigger. For a fast
second rate, the initial concentration can be way above equilibrium
and the high concentration may promote second nucleation to occur
along with crystal growth. Nucleation rate is high when the
concentration is high, so both nucleation and growth are rapid.
Because of that, most likely the secondary nucleation and growth
will not form stable crystals or create amorphous, which can be
removed.
[0066] The route to forming the smallest and highest quality PZT
nanoparticles is achieved using the shortest possible processing
time for the hydrothermal processing, which includes using the
highest heating ramp rate, the fastest cooling ramp rate, and a
"medium" mineraliser concentration, since the required processing
time will be different if the mineraliser concentration is changed.
For example, if 5M mineraliser is used, the processing time can be
as short as one (1) hour but for 2M mineraliser, the required
processing time is three (3) hours. If the mineraliser
concentration is lower at 0.4M, no PZT will be formed regardless of
the processing time.
[0067] After the cooling step, a PZT nanoparticle solution is
obtained. The PZT nanoparticle solution contains a plurality of PZT
nanoparticles suspended in water. The PZT nanoparticle solution can
be filtered or otherwise manipulated to isolate the PZT
nanoparticles. Depending on the efficiency of the hydrothermal
process, the solution may also contain PbTiO.sub.3, PbZrO.sub.3,
PbO, TiO.sub.2, ZrO.sub.2, KOH or other potential impurities.
Washing the solution with acetic acid is one method for removing
PbO. Excess lead samples may be washed with acetic acid.
[0068] As shown in FIG. 5, the system 100 further comprises an ink
deposition apparatus 142 (see also FIG. 6A) that deposits the PZT
nanoparticle ink 104 onto a substrate 101 to form the PZT
nanoparticle ink based piezoelectric sensor 110. The ink deposition
apparatus 142 and an ink deposition process 122 using the ink
deposition apparatus 142 do not require growth of PZT crystals 166
(see FIG. 6B) on the substrate 101. Because the PZT crystals 166
have already been grown in the PZT nanoparticles, the PZT
nanoparticle ink 104 does not require a high temperature sintering
process once deposited during the ink deposition process 122. The
ink deposition apparatus 142 preferably comprises a direct write
printing apparatus 144 (see FIG. 10). FIG. 10 is an illustration of
a block diagram of embodiments of the ink deposition apparatuses
and processes that may be used to fabricate the PZT nanoparticle
ink based piezoelectric sensor 110 of the disclosure. As shown in
FIG. 10, the direct write printing apparatus 144 may comprise a
jetted atomized deposition apparatus 146, an ink jet printing
apparatus 147, an aerosol printing apparatus 190, a pulsed laser
evaporation apparatus 192, a flexography printing apparatus 194, a
micro-spray printing apparatus 196, a flat bed silk screen printing
apparatus 197, a rotary silk screen printing apparatus 198 or
another suitable screen printing apparatus, a gravure printing
apparatus 199 or another suitable press printing apparatus, or
another suitable direct write printing apparatus 144.
[0069] The PZT nanoparticle ink 104 may be deposited onto the
substrate 101 with the ink deposition apparatus 142 via an ink
deposition process 122 (see FIGS. 6A and 10). The ink deposition
process 122 preferably comprises a direct write printing process
124 (see FIG. 10). As shown in FIG. 10, the direct write printing
process 124 may comprise a jetted atomized deposition process 126,
an ink jet printing process 128, an aerosol printing process 180, a
pulsed laser evaporation process 182, a flexography printing
process 184, a micro-spray printing process 186, a flat bed silk
screen printing process 187, a rotary silk screen printing process
188 or another suitable screen printing process, a gravure printing
process 189 or another suitable press printing, or another suitable
direct write printing process 124.
[0070] As shown in FIG. 5, the substrate 101 may have a non-curved
or planar surface 136, a curved or non-planar surface 138, or a
combination of a non-curved or planar surface 136 and a curved or
non-planar surface 138. As shown in FIG. 2, the substrate 101 may
have a first surface 103a and a second surface 103b. The substrate
101 preferably comprises a composite material, a metallic material,
a combination of a composite material and a metallic material, or
another suitable material. As shown in the FIG. 2, the substrate
101 may comprise a composite structure 102. The composite structure
102 may comprise composite materials such as polymeric composites,
fiber-reinforced composite materials, fiber-reinforced polymers,
carbon fiber reinforced plastics (CFRP), glass-reinforced plastics
(GRP), thermoplastic composites, thermoset composites, epoxy resin
composites, shape memory polymer composites, ceramic matrix
composites, or another suitable composite material. As shown in
FIG. 3, the substrate 101 may comprise a metallic structure 132.
The metallic structure 132 may comprise metal materials such as
aluminum, stainless steel, titanium, alloys thereof, or another
suitable metal or metal alloy. The substrate 101 may also comprise
another suitable material.
[0071] FIG. 6A is an illustration of a schematic view of one of the
embodiments of an ink deposition process 122 and an ink deposition
apparatus 142 for fabricating the PZT nanoparticle ink based
piezoelectric sensor 110 of the disclosure. An exemplary direct
write printing process 124 and direct write printing apparatus 144
are shown in FIG. 6A, which shows the jetted atomized deposition
process 126 and the jetted atomized deposition apparatus 146. As
shown in FIG. 6A, nanoscale PZT ink nanoparticles 106 may be
transferred via an inlet 148 into a mixing vessel 150 containing a
solvent 152. The nanoscale PZT ink nanoparticles 106 are preferably
mixed with the solvent 152 in the mixing vessel to form a PZT
nanoparticle ink suspension 154. The PZT nanoparticle ink
suspension 154 may be atomized by an ultrasonic mechanism 158 to
form atomized PZT ink nanoparticles 156. The atomized PZT ink
nanoparticles 156 may then be transferred through a nozzle body 160
and directed through a nozzle tip 162 to the substrate 101 for
depositing and printing of the PZT nanoparticle ink based
piezoelectric sensor 110 onto the substrate 101.
[0072] FIG. 6B is an illustration of a close-up view of the PZT
piezoelectric nanoparticle ink based sensor 110 being deposited on
the substrate 101. FIG. 6B shows the atomized PZT ink nanoparticles
156 in the nozzle body 160 and the nozzle tip 162 being deposited
onto the substrate 101 to form the PZT nanoparticle ink based
piezoelectric sensor 110. As shown in FIG. 6B, the PZT nanoparticle
ink based piezoelectric sensor or sensors 110 may be deposited onto
the substrate 101 in a customized shape 164, such as letters,
designs, logos, or insignias, or geometric shapes such as circles,
squares, rectangles, triangles, or other geometric shapes, or
another desired customized shape. The ink deposition process 122
and the ink deposition apparatus 142 do not require growth of PZT
crystals 166 on the substrate 101. Moreover, the deposited
nanoscale PZT ink nanoparticles 106 contain a crystalline particle
structure that does not require any post processing steps to grow
the crystals. The PZT nanoparticle ink based piezoelectric sensor
110 may be deposited onto a surface of the structure 30 with one or
more layers of insulation, coatings, or paint in between a body of
the structure 30 and the PZT nanoparticle ink based piezoelectric
sensor 110.
[0073] FIGS. 2 and 3 show embodiments of a deposited PZT
nanoparticle ink based piezoelectric sensor assembly 115. FIG. 2 is
an illustration of a cross-sectional view of one of the embodiments
of a deposited PZT nanoparticle ink based piezoelectric sensor
assembly 116 that is deposited onto a substrate 101 comprising a
composite structure 102. The deposited PZT nanoparticle ink based
piezoelectric sensor assembly 116 comprises the PZT nanoparticle
ink based piezoelectric sensor 110 coupled to a power and
communication wire assembly 140 acting as an actuator 141 (see FIG.
4). The power and communication wire assembly 140 is preferably
formed of a conductive ink 168 (see FIG. 4) that may be deposited
via the ink deposition apparatus 142 and via the ink deposition
process 122 onto the substrate 101. The power and communication
wire assembly 140 acting as an actuator 141 (see FIG. 4) may
comprise a first conductive electrode 114, a second conductive
electrode 118, a first conductive trace wire 112a, and a second
conductive trace wire 112b. The first conductive electrode 114, the
second conductive electrode 118, the first conductive trace wire
112a, and the second conductive trace wire 112b may be adjacent to
the PZT nanoparticle ink based piezoelectric sensor 110.
[0074] FIG. 3 is an illustration of a cross-sectional view of
another one of the embodiments of a deposited PZT nanoparticle ink
based piezoelectric sensor assembly 130 that is deposited onto a
substrate 101 comprising a metallic structure 132. The deposited
PZT nanoparticle ink based piezoelectric sensor assembly 130
comprises the PZT nanoparticle ink based piezoelectric sensor 110
coupled to a power and communication wire assembly 140 acting as an
actuator 141 (see FIG. 4). The power and communication wire
assembly 140 is preferably formed of a conductive ink 168 (see FIG.
4) that may be deposited via the ink deposition apparatus 142 and
via the ink deposition process 122 onto the substrate 101. The
power and communication wire assembly 140 acting as the actuator
141 may comprise the first conductive electrode 114, the second
conductive electrode 118, the first conductive trace wire 112a, and
the second conductive trace wire 112b. The first conductive
electrode 114, the second conductive electrode 118, the first
conductive trace wire 112a, and the second conductive trace wire
112b may be adjacent to the PZT nanoparticle ink based
piezoelectric sensor 110. As shown in FIG. 3, the deposited PZT
nanoparticle ink based piezoelectric sensor assembly 130 further
comprises an insulation layer 134 deposited between the substrate
101 comprising the metallic structure 132 and the PZT nanoparticle
ink based piezoelectric sensor 110 coupled to the power and
communication wire assembly 140. The insulation layer 134 may
comprise an insulating polymer coating, a dielectric material, a
ceramic material, a polymer material, or another suitable
insulation material.
[0075] FIG. 4 is an illustration of a top perspective view of the
deposited PZT nanoparticle ink based piezoelectric sensor assembly
115 deposited on a composite structure 102. FIG. 4 shows a
plurality of PZT nanoparticle ink based piezoelectric sensors 110
coupled to a plurality of power and communication wire assemblies
140, all deposited on the composite structure 102. Similarly, for a
metallic structure 132, the deposited PZT nanoparticle ink based
piezoelectric sensor assembly 130 may have a plurality of PZT
nanoparticle ink based piezoelectric sensors 110 coupled to a
plurality of power and communication wire assemblies 140, all
deposited on the metallic structure 132.
[0076] The deposition of the PZT nanoparticle ink based
piezoelectric sensors 110 on the substrate 101 or structure 30 (see
FIG. 7) enables in situ installation of the PZT nanoparticle ink
based piezoelectric sensors 110 for applications such as structural
health monitoring. The PZT nanoparticle ink based piezoelectric
sensors 110 may be a key enabler of high density structural health
monitoring systems 170. FIG. 7 is an illustration of a block
diagram of one of the embodiments of a structural health monitoring
system 170 using the PZT nanoparticle ink based piezoelectric
sensors 110 of the disclosure. Two or more nanoparticle ink based
piezoelectric sensors 110 may be used to enable the structural
health monitoring system 170 for monitoring structural health 172
of a structure 30, such as a composite structure 102 (see FIG. 1)
or a metallic structure 132 (see FIG. 3), or another suitable
structure, and providing structural health data 174. The structural
health data 174 may comprise disbonds, weak bonding, strain levels,
moisture ingression, materials change, cracks, voids, delamination,
porosity, or other suitable structural health data 174 or
electromechanical properties or other irregularities which may
adversely affect the performance of the structure 30.
[0077] The structural health monitoring system 170 preferably
comprises a deposited PZT nanoparticle ink based piezoelectric
sensor assembly 115 (see also FIGS. 2 and 3). The deposited PZT
nanoparticle ink based piezoelectric sensor assembly 115 may
comprise the deposited PZT nanoparticle ink based piezoelectric
sensor assembly 116 (see FIG. 2), if used with the composite
structure 102, and may comprise the deposited PZT nanoparticle ink
based piezoelectric sensor assembly 130 (see FIG. 3), if used with
a metallic structure 132. The structural health monitoring system
170 may further comprise a voltage supply source 176 that may be
used for poling the PZT nanoparticle ink based piezoelectric sensor
110 prior to use in the structural health monitoring system 170. As
used herein, the term "poling" means a process by which a strong
electric field is applied across a material, usually at elevated
temperatures, in order to orient or align dipoles or domains. The
voltage supply source 176 may also drive some PZT nanoparticle ink
based piezoelectric sensors 110 so that they become actuators 141
sending interrogating signals to other piezoelectric sensors
110.
[0078] As shown in FIG. 7, the structural health monitoring system
170 further comprises an electrical power source 178 for providing
electrical power to the PZT nanoparticle ink based piezoelectric
sensors 110. The electrical power source 178 may comprise
batteries, voltage, RFID (radio frequency identification), magnetic
induction transmission, or another suitable electrical power
source. The electrical power source 178 may be wireless. As shown
in FIG. 7, the system 170 may further comprise a digital data
communications network 179 for retrieving and processing structural
health data 174 from the PZT nanoparticle ink based piezoelectric
sensors 110. The digital data communications network 179 may be
wireless. The digital data communications network 179 may retrieve
data received from the PZT nanoparticle ink based piezoelectric
sensors 110, such as with a receiver (not shown), and may process
data received from the PZT nanoparticle ink based piezoelectric
sensors 110, such as with a computer processor (not shown). The
digital data communications network 179 may be wireless.
[0079] In an embodiment of the disclosure, there is provided a
method 200 of fabricating a lead zirconate titanate (PZT)
nanoparticle ink based piezoelectric sensor 110. FIG. 8 is an
illustration of a flow diagram of an embodiment of the method 200
of the disclosure. The method 200 comprises step 202 of formulating
a lead zirconate titanate (PZT) nanoparticle ink 104. The PZT
nanoparticle ink 104 comprises nanoscale PZT ink nanoparticles 106.
As discussed above, the PZT nanoparticle ink 104 preferably has a
nanoscale PZT particle size in a range of from about 20 nanometers
to about 1 micron. The PZT nanoparticle ink 104 may comprise a
sol-gel based adhesion promoter 108 (see FIG. 5) for promoting
adhesion of the PZT nanoparticle ink 104 to the substrate 101. The
PZT nanoparticle ink 104 is formulated via the process as discussed
in detail above.
[0080] The method 200 further comprises step 204 of depositing the
PZT nanoparticle ink 104 onto the substrate 101 via an ink
deposition process 122 to form the PZT nanoparticle ink based
piezoelectric sensor 110. The ink deposition process 122 preferably
comprises a direct write printing process 124 (see FIG. 10). As
shown in FIG. 10, the direct write printing process 124 may
comprise a jetted atomized deposition process 126, an ink jet
printing process 128, an aerosol printing process 180, a pulsed
laser evaporation process 182, a flexography printing process 184,
a micro-spray printing process 186, a flat bed silk screen printing
process 187, a rotary silk screen printing process 188 or another
suitable screen printing process, a gravure printing process 189 or
another suitable press printing, or another suitable direct write
printing process.
[0081] The substrate 101 preferably comprises a composite material,
a metallic material, a combination of a composite material and a
metallic material, or another suitable material. The substrate 101
preferably comprises a first surface 103a and a second surface
103b. The substrate 101 may have a non-curved or planar surface 136
(see FIG. 5), a curved or non-planar surface 138 (see FIG. 5), or a
combination of a non-curved or planar surface 136 (see FIG. 5) and
a curved or non-planar surface 138 (see FIG. 5). The ink deposition
process 122 does not require growth of PZT crystals 166 on the
substrate 101. Moreover, the deposited nanoscale PZT ink
nanoparticles 106 contain a crystalline particle structure which
does not require any post processing steps to grow the crystals.
The PZT nanoparticle ink based piezoelectric sensor 110 may be
deposited onto the substrate 101 in a customized shape 164 (see
FIG. 6B).
[0082] The PZT nanoparticle ink based piezoelectric sensor 110 may
undergo a poling process with a voltage supply source 176 (see FIG.
7) prior to being used in the structural health monitoring system
170 for monitoring structural health 172 of a structure 30. The PZT
nanoparticle ink based piezoelectric sensor 110 may be coupled to a
power and communication wire assembly 140 formed from a conductive
ink 168 deposited onto the substrate 101 via the ink deposition
process 122 prior to being used in the structural health monitoring
system 170. Two or more PZT nanoparticle ink based piezoelectric
sensors 110 may be used to enable the structural health monitoring
system 170.
[0083] In another embodiment of the disclosure, there is provided a
method 250 of fabricating a lead zirconate titanate (PZT)
nanoparticle ink based piezoelectric sensor 110. FIG. 9 is an
illustration of a flow diagram of another embodiment of the method
250 of the disclosure. The method 250 comprises step 252 of
formulating a lead zirconate titanate (PZT) nanoparticle ink 104
comprising nanoscale PZT ink nanoparticles 106 that are
pre-crystallized.
[0084] The method 250 further comprises step 254 of suspending the
PZT nanoparticle ink 104 in a sol-gel based adhesion promoter 108.
The method 250 further comprises step 256 of depositing the PZT
nanoparticle ink 104 onto a substrate 101 via a direct write
printing process 124 to form a PZT nanoparticle ink based
piezoelectric sensor 110. As shown in FIG. 10, the direct write
printing process 124 may comprise a jetted atomized deposition
process 126, an ink jet printing process 128, an aerosol printing
process 180, a pulsed laser evaporation process 182, a flexography
printing process 184, a micro-spray printing process 186, a flat
bed silk screen process 187, a rotary silk screen process 188 or
another suitable screen printing process, a gravure printing
process 189 or another suitable press printing, or another suitable
direct write printing process 124.
[0085] The substrate 101 preferably comprises a composite material,
a metallic material, a combination of a composite material and a
metallic material, or another suitable material. The substrate 101
preferably comprises a first surface 103a and a second surface
103b. The substrate 101 may have a non-curved or planar surface 136
(see FIG. 5), a curved or non-planar surface 138 (see FIG. 5), or a
combination of a non-curved or planar surface 136 (see FIG. 5) and
a curved or non-planar surface 138 (see FIG. 5). The ink deposition
process 122 does not require growth of PZT crystals 166 on the
substrate 101. Moreover, the deposited nanoscale PZT ink
nanoparticles 106 contain a crystalline particle structure which
does not require any post processing steps to grow the crystals.
The PZT nanoparticle ink based piezoelectric sensor 110 may be
deposited onto the substrate 101 in a customized shape 164 (see
FIG. 6B).
[0086] The PZT nanoparticle ink based piezoelectric sensor 110 may
undergo a poling process with a voltage supply source 176 prior to
being used in the structural health monitoring system 170 for
monitoring structural health 172 of a structure 30. The PZT
nanoparticle ink based piezoelectric sensor 110 may be coupled to a
power and communication wire assembly 140 formed from a conductive
ink 168 deposited onto the substrate 101 via the ink deposition
process 122 prior to being used in the structural health monitoring
system 170. Two or more PZT nanoparticle ink based piezoelectric
sensors 110 may be used to enable the structural health monitoring
system 170.
[0087] The structure 30 may comprise an aircraft, a spacecraft, an
aerospace vehicle, a space launch vehicle, a rocket, a satellite, a
rotorcraft, a watercraft, a boat, a train, an automobile, a truck,
a bus, an architectural structure, a turbine blade, a medical
device, electronic actuation equipment, a consumer electronic
device, vibratory equipment, passive and active dampers, or another
suitable structure. The system 100 and methods 200, 250 may be used
across many industries including, for example, wind power
generation (health monitoring of turbine blades), aerospace
applications, military applications, medical applications,
electronic actuation equipment, consumer electronic products, or
any application where structures or materials require a monitoring
system.
[0088] Embodiments of the system 100 and methods 200, 250 disclosed
herein for fabricating the PZT nanoparticle ink based piezoelectric
sensors 110 provide PZT nanoparticle ink based piezoelectric
sensors 110 that may be used for a variety of applications
including ultrasonic damage detection for composite and metallic
structures, crack propagation detection sensors, pressure sensors,
or another suitable sensor. For example, the PZT nanoparticle ink
based piezoelectric sensors 110 of the system 100 and methods 200,
250 provide cradle to grave health monitoring of various components
in aircraft such as damage detection for door surrounds, military
platforms such as crack growth detection for military aircraft, and
space systems such as cryo-tank health monitoring. The PZT
nanoparticle ink based piezoelectric sensors 110 may provide data
that was previously not available that may influence new and
efficient designs which may reduce costs.
[0089] Using the direct write printing process 124, and for
example, the jetted atomized deposition process 126, along with the
formulated PZT nanoparticle ink 104, allows many PZT nanoparticle
ink based piezoelectric sensors 110 to be deposited onto a
substrate 101 or structure 30 and at a decreased cost as compared
to known piezeoelectric sensors. Embodiments of the system 100 and
methods 200, 250 disclosed herein provide PZT nanoparticle ink
based piezoelectric sensors 110 that allow for the placement of the
PZT nanoparticle ink based piezoelectric sensors 110 in numerous
areas of a structure and at large quantities, both of which may be
difficult with known piezoelectric sensors. Moreover, embodiments
of the system 100 and methods 200, 250 disclosed herein for
fabricating the PZT nanoparticle ink based piezoelectric sensors
110 provide PZT nanoparticle ink based piezoelectric sensors 110
that are advantageous to known sensors because they do not require
an adhesive to bond them to the structure, and this decreases the
possibility that the PZT nanoparticle ink based piezoelectric
sensors 110 may disbond from the structure. Embodiments of the
system 100 and methods 200, 250 disclosed herein for fabricating
the PZT nanoparticle ink based piezoelectric sensors 110 provide
PZT nanoparticle ink based piezoelectric sensors 110 that are
enabled by the availability of nanoscale PZT ink nanoparticles 106
having favorable piezoelectric properties and that are deposited
onto a substrate or structure in a desired configuration for use
without the use of adhesive. Because the PZT nanoparticle ink based
piezoelectric sensors 110 may be deposited onto a substrate or
structure with no adhesive between the PZT nanoparticle ink based
piezoelectric sensors 110 and the substrate or structure, improved
signal coupling into the structure being interrogated may be
achieved. Further, embodiments of the system 100 and methods 200,
250 disclosed herein for fabricating the PZT nanoparticle ink based
piezoelectric sensors 110 provide PZT nanoparticle ink based
piezoelectric sensors 110 do not require manual placement or
installation on the substrate or structure and may be deposited or
printed onto the substrate or structure, along with all the
required power and communication wire assemblies, thus decreasing
labor and installation costs, as well as decreasing complexity and
weight of the structure. In addition, the PZT nanoparticle ink
based piezoelectric sensors 110 may be fabricated from numerous
direct write printing processes, including the jetted atomized
deposition process 126; may be fabricated from nanoparticle size
particles which have been pre-crystallized and may be more
efficient than known sensors that have not been crystallized; do
not require a high temperature sintering/crystallization process
and thus reduce or eliminate possible damage to temperature
sensitive substrates or structures; may be deposited onto curved or
non-planar substrates or structures; have no or minimal physical
geometry limitations and thus decrease the possibility of
inadequate sensing capacities or inadequate actuation responses.
Finally, embodiments of the system 100 and methods 200, 250
disclosed herein for fabricating the PZT nanoparticle ink based
piezoelectric sensors 110 provide PZT nanoparticle ink based
piezoelectric sensors 110 that may be used to predict deterioration
or weaknesses of a structure prior to the actual development of
such deterioration or weaknesses, and thus, may increase
reliability of the structure or structural component parts, and may
reduce overall manufacturing and maintenance costs over the life of
the structure or structural component parts; and that have the
ability to predict, monitor, and diagnose the integrity, health,
and fitness of a structure without having to disassemble or remove
the structure or drill holes into the structure for insertion of
any measurement tools.
[0090] Many modifications and other embodiments of the disclosure
will come to mind to one skilled in the art to which this
disclosure pertains having the benefit of the teachings presented
in the foregoing descriptions and the associated drawings. The
embodiments described herein are meant to be illustrative and are
not intended to be limiting or exhaustive. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
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